The overall goal of the experiments proposed in this Project is to study the role of the CREB system in Purkinje cell synaptic plasticity in the cerebellar cortex. The CREB system was selected for analysis in the cerebellum because of the large accumulation of evidence from diverse systems and species demonstrating that this group of transcriptional factors has a critical role in signaling between the synapse and the nucleus. Given the specificity of the Pcp-2/L7 regulatory elements to direct expression to Purkinje cells, the experimental approach to be used offers a distinct advantage in that it will enable us to examine the role of CREB in a select population of neurons within the mammalian brain. Furthermore, these experiments will enable an activator form of CREB to be expressed in Purkinje cells providing the first direct test of CREB activator function in a mammalian neuronal cell type. It should also be noted that all transgenic mice will be generated using an inbred strain, FVB/n. Thus, there will be no variation in genetic background between littermates except for that due to the presence or absence of the transgene. Finally, demonstrating a functional importance for CREB in the cerebellar cortex will provide important molecular support that this region of the brain is involved in motor learning. The specific aims to be pursued are: 1) To examine whether the disruption of CREBs within Purkinje cells of the cerebellar cortex alters their function and morphology. This will be accomplished by the over-expression of ICER in Purkinje cells in transgenic mice using Pcp-2 regulatory elements. 2) To use a regulatable model of ICER expression to directly correlate disruption in CREB with alterations in Purkinje cell function. 3) To further examine the role of CREB in Purkinje cell function, we will establish transgenic mice with induced expression of a CREB activator isoform.